Slitter-disk bark-stripping apparatus



June 23, 1959 w. M. ALLEN 2,891,588

'SLITTER-DISK- BARK-STRIPPING APPARATUS Fi led Feb. 26. 1958 i1 Mimi m;

INVENTOR- WILLIAM M. ALL EN United States Patent SLITTER-DISKBARK-STRIPPING APPARATUS William M. Allen, Columbus, Ohio, assignor toBattelle Memorial Institute, Columbus, Ohio, a corporation of OhioApplication February 26, 1958, Serial No. 717,698

13 Claims. (Cl. 144--208) This invention relates to apparatus forremoving bark from logs and slabs. More particularly, it relates toapparatus for removing the bark from log and slab portions of logs bythe method of stripping the bark from the log in continuouslylongitudinal progression.

Two of the most well-known manners of removing bark from logs are: (1)chipping the bark away from the surface of the log or slab by means of aplurality of knives arranged to cut and extract the bark in smallfragments or chips; and (2) the use of knives and wedge plates arrangedto pass longitudinally with respect to the axis of the slab or log andto cut from and wedge beneath the bark.

Usually, in the method of (l), rapidly rotating knives are provided andthe bark is removed in small segments by the chiseling effect of theknives. On the other hand, in the method of (2), the bark islongitudinally separated into longitudinal segments after which atearing or wedging force is created between the bark and the wood of thetree, at the position of the cambium layer. The wedging force overcomesthe tension in this layer and the bark peels away from the wood at thenatural line of separation between the two.

This invention relates to apparatus for accomplishing this latter methodmoresuccessfully and with greater efficiency than previously known.

Briefly, in this invention rotatable slitter disks of a particular andcritical configuration are disclosed which arev adapted to roll upon thesurface of the log while cutting segments of bark and peeling thesesegments of the bark from the wood by wedging the bark laterally. Thesedisks are provided with a rolling contact surface having a beveledportion tapering from one side toward the other to meet a cuttingportion projecting radially from the beveled surface. These disks areheld at a particular specified attitude or position with respect to thelog and bark. The disks of this invention are in a canted and toe-inposition with respect to a longitudinally disposed radial plane of thelog.

Difficulty has been experienced in the past in peeling the bark fromlogs because of the varying tightness with which it sticks to the logduring different seasons of the year. Timber which is cut in the springand summer may be easily debarked by the peeling method because of therelative ease with which the bark breaks away from the tree at thecambium layer. On the other hand, logs which are cut in the fall andwinter of the year have proven to be very difiicult to debark by peelingmethods. In addition to the tenacity between the bark and the wood inthe cambium area at this time of the year, in

many instances the bark is filled with moisture that is frozen, holdingthe bark in place. Insofar as is known, the conventional bark-peelingapparatus, such as wedges and knife-edge cutters, have not proven to besuccessful in more than a'lim'ited number of applications whereconditions are decidedly favorable. Debarking in the Winter time by thismethod has been very unsuccessful.

Another difliculty is that different species of woods debarkdifferently.

It is therefore an object of this invention to provide apparatus whichmay be successfully operated on a variety of difierent species of woodincluding white pine, yellow pine, and fir during both the winter seasonand the summer season. It is a further purpose to provide apparatus forpeeling the bark from logs and slabs that is compact and sufiicientlyportable to be taken apart into smaller components and easilytransported. It is an object of the inventionv to provide bark-removingapparatus which will cleanly remove the bark from the log leaving a veryminimum bark contamination on the log.

To these and other ends, this invention comprises apparatus, thepreferred form of which is disclosed in the following description andattached drawings. Although the apparatus and structure described andshown in detail refer with particularity to a machine for stripping thebark from portions of log or slabs, it is apparent that this inventionshould not be limited thereto. Many of the significant details ofthis'invention applied with equal qualification may be applicable toshavers in other branches of technical endeavor. The invention may beused for other purposes where its features are advantageous,

In the drawings:

Fig. l is a plan view of the general layout'of the apparatus of thisinvention;

Fig. 2 is an elevation of the apparatus shown in Fig. 1;

Fig. 3 is a fragmentary enlarged-scale, vertical section taken on theline 3-3 of Fig. l, and shows a schematic diagram of the slitter disk ofthis invention in operative position; I I

Fig. 4 is a plan view of the slitter disk at the same position; and

Fig. 5 is an enlarged elevation of a portion of the rolling contactsurface of the slitter disk of this invention. 1

The apparatus of this invention to be described in detail isspecifically adapted to debark slabs of logs. However, it should be'understood that the apparatus is equally applicable to debarking fulllog segments, since slabs is the name conventionally used for portions'of a log obtained by cutting ona chord of the circular cross sectionofthe log. t

Referring to Fig. l, .the apparatus disclosed comprises two cooperativeportions. A debarker portion 10 is at the entrance end of the apparatus.A chipper portion 11 is positioned to receive debarked slabs and reducethem to chips.

The debarker unit 10 comprises a centrally positioned, substantiallyhorizontal conveyor 12 supported in a frame 13 and driven by a gearmotor 14 at one end. The conveyor 12 is positioned to receive at one end17 a slab 15 with bark 16 in place as shown. The slabs 15 are placed onthe conveyor 12 with their longitudinal axes parallel to thelongitudinal axis of the conveyor 12. In order to provide a grip on theslab 15, the surface of conveyor 12 has means to engage and press intothe surface of the slab 15. This means may be a plurality of protrudingpins 25. Slabs 15 are first conveyed beneath a pressure roll 18 whichholds the slabs firmly in contact with the conveyor belt 12. Secondly,the conveyor belt 12 carries the slabs 15 beneath a plurality of slitterdisks 19, 20, 21, 22, and 23. As most clearly seen in Figs. 1 and 2, theslitterdisks 19-23 are positioned in progressively spaced'relationlongitudinally along the path of travel of the slab 15. In a manner thatis described in detail later herein, the disks 19-23 roll on the slab 15as it progresses beneath them, and the bark 16 *is loosened and peeledfrom the wood.

After passing beneath the slitter disks 19-23, the slab is carriedbeneath a pair of brushes 24 which are supported from an upper portion57 of the frame 13 (Fig. 2). The brushes 24 serve to push the bark 16that has been freed by the slitter disks 19-23 laterally to the edges ofthe slab 15 where it falls on the surface of a chute 26 at either sideof the conveyor 12.

Leaving the brushes 24, slab 15 passes beneath a second pressure roll 27which assures that there is a firm contact between the bottom of theslab 15 and conveyor belt 12 so that the slab 15 is firmly held andprogresses with the belt 12. The continued progression of slab 15carries it beneath a driven wheel 30 as it leaves the end of conveyor12. The driven wheel 31 may be conveniently operated through a chaindrive 36 by the gear motor 14. The wheel 30 forces the end of the slabinto the path of a plurality of rapidly rotating chipping knives 31which are supported on a fiywheel 32 that is driven by an electric motor33. The speed and force of the chipping knives causes the end of theslab to be flaked into a large quantity of chips which is carried bymomen tum out through an aperture 34 in an enclosure 35 which surroundsthe chipping wheel 32. The aperture 34 may be connected in communicationwith a storage bin or place where the chips are used.

This invention is primarily concerned with the barkremoval portion ofthe apparatus 10. It has been found that the bark may be removed fromwhite pine, yellow pine, and fir during both the winter and summerseason by the apparatus of this invention including slitter disks 19-23having a rolling contact surface of the following configuration.

The slitter disks 19-23 are constructed with a rim portion 41) having abeveled surface 41 tapered to meet a cutter side 44 in an acute angle a.An annular cutting portion 43 protrudes radially outward beyond thebeveled surface 41. Tests have shown that the configuration of the rimis more than a matter of choice. It has been found that the portion 41should be beveled at a very large acute angle and that an angle of about70 degrees for or gives optimum results. The provision of a large acuteangle makes the beveled surface 41 act as a flange to some degree, andprevents the cutting portion 43 from penetrating too deeply. It has alsobeen found that, in a typical slitter disk having a thickness of about/1 inch from one side 42 to the other side 44, the cutting portion 43should protrude beyond the surface of the beveled surface 41 about Ainch. The optimum protrusion is therefore about of the width of the rim40.

In the operation of the slitter disk, a slab 15 is carried in a linearpath past the position of the disk. Slab 15 is held so that the line oftravel of the cutting portion 13 enters the bark 16 and cuts a groovetherein. Simultaneously, the beveled surface 41 exerts a lateral forceon the bark while the wood of the slab 15 is prevented from lateralmovement. This provides a shearing force in the cambium layer where thebark 16 is attached to the wood of the slab 15 causing a lateralrupture. Bark 16 is displaced laterally and thereby removed from itspositions on the wood.

The apparatus for holding the slitter disks 19-23 cornprises means forresiliently forcing these members into contact with the bark 16 andmeans for holding the shafts upon which the disks rotate in position tomove radially with respect to the center of curvature of the surface ofthe slab without movement either tangentially or longitudinally.

Referring to Fig. 2, the means for resiliently holding and forcing theslitter disks 19-23 toward the slab may comprise air cylinders operatingpiston rods 51 which support the slitter disks 19-23 in yokes 52.

The means for supporting slitter disks 19-23 in the opposite directionmay comprise a plurality of swingable arms 53 rotatively supporting theshafts of the slitter disks 19-23 at one end 54. The arms 53 arepivotally supported at the opposite end 55 by a plate 56 which isconnected to the upper portion 57 of the frame 13. The cylinders 50 maybe connected to a source of compressed air at adjustable pressure. As aslab 15 makes initial contact with the first two slitter disks 19 and2d, the end of the slab and the bark lifts them up. The lifting actionon the disks 19 and 211 is resisted by the resilient compressible forceexerted by the air pressure in the piston 50. The slitter disks 1.9 and211 are guided in their upward movement by the swinging action of arms53. The amount of pressure exerted by the rolling contact surface 411 ofthe slitter disks 19-23 may be adjustably controlled by the amount ofair pressure in the pistons 51).

In the apparatus of the example, slitter disks 20, 22, and 23 arepositioned with the cutting portion 43 at one side. Slitter disks 19 and21 are oppositely positioned. The disks 2%, 22, and 23 move the barklaterally to one side, while on the other hand, disks 19 and 21 move thebark in the opposite direction.

in addition to the significant improvement in the results obtained inthe use of this debarking apparatus by means of the configuration of therim 40 that has been disclosed, it has been found that results can befurther improved by supporting slitter disks 19-23 in a particularposition with respect to the surface of the slabs 15 and with respect tothe line of travel or path of movement of these slabs 15.

Referring to Figs. 3 and 4, slab 15 is indicated as having asubstantially curved outer surface covered by bark 16 at one side of theslitter disk 23. It will be understood, of course, that the designationof the slitter disk 23 in Figs. 3 and 4 is by way of example only, asall of the slitter disks 19-23 are of similar construction and operatedin the same manner.

By way of illustration, slab 15 in Fig. 3 is considered to be passingaway from the viewer and the axis 54 of slitter disk 23 may beconsidered to be stationary. In a like manner, in Fig. 4 the axis 54 ofslitter disc 23 may be considered stationary, and slab 15 is movingtoward the two arrows with respect thereto. It has been found that inorder to obtain optimum debarking action as slitter disk 23 moves alongthe surface of the wood, making contact at a momentary point 60 on alongitudinally disposed radial plane represented by the line 61, thedisk 23 should be at a canted position with respect to the plane 61 atan angle 6 (Fig. 3). An angle 6 of about 15 has been found to beeffective. It has also been found that the disk 23 should be toed in atan angle (Fig. 4) with respect to the plane 61. An angle of about 15 hasbeen found to be effective. During the passage of the slab 15 beneaththe disk 23, the frictional resistance of the rim 40 on the bark 16 andwood of the slab 15 causes the disk 23 to roll without the provision ofany external power applied thereto. The rolling action with the cantedand toe-in position of the disk 23, together with the beveled surface 41and the cutting portion 43 provide a unified cutting, twisting, wedgingforce on the bark. This has been found to effectively strip the barkfrom the wood cleanly under the most adverse conditions. For example,freshly cut slabs from trees felled during the month of January weredebarked by the apparatus of this invention cleanly to the surface ofthe wood at the cambium layer at a rate of progress along the surface ofthe wood of llO feet per minute. This operation Was carried outrepeatedly with similar results in which the bark remaining before thedebarked slabs had been re duced to chips was only 0.2 percent. Testswith debarkers of other configurations, such as sharply pointed andangled edges, showed 8.7 percent remaining bark.

It will be understood, of course, that, while the forms of the inventionherein shown and described constitute the preferred embodiments of theinvention, it is not intended herein to illustrate all of the possibleequivalent forms or ramifications of the invention. It will also beunderstood that the words used are words of description, rather than oflimitation, and that various changes, such as changes in shape, relativesize, and arrangement of parts may be substituted without departing fromthe function or scope of the invention herein disclosed.

What is claimed is: V

1. Apparatus for removing bark from a log comprising: a first supportand a second support movable with respect thereto; said second supportconstructed to receive and firmly hold a workpiece portion of a log withthe bark in place on the log as grown; a disk carried by the firstsupport in a position of rolling contact on said log portion as saidsecond support moves with respect to said first support; a rollingcontact surface on said disk including a beveled portion tapering fromone side toward the other and meeting a cutting portion; said disk beingheld in a canted position with respect to a tangent plane at thecircumference of the log and said disk being toed in with respect to theline of the travel of said log portion.

2. Apparatus for removing bark from a log comprising: a first supportand a second support movable linearly with respect thereto; said secondsupport constructed to receive and firmly hold a workpiece portion of alog having the bark in place on the log as grown, in position with thelongitudinal axis of the log substantially parallel to the line ofmovement between said first and second supports; a disk carried by saidfirst support in a position of rolling contact on said log portion assaid second support moves with respect to said first support; a rollingcontact surface on said disk including a beveled portion tapering fromone side toward the other and meeting a cutting portion; said disk beingheld in a canted position with respect to a tangent plane at thecircumference of the log and said disk being toed in with respect to theline of the travel of said log portion.

3. Apparatus for removing bark from a log comprising: a first supportand a second support movable linearly with respect thereto; said secondsupport constructed to receive and firmly hold a workpiece portion of alog having the bark in position on the log as grown, in position withthe longitudinal axis of the log substantially parallel to the line ofmovement between said first and second supports; a disk carried by saidfirst support in a position of rolling contact on said log and rollingby frictional resistance on the bark of said log as the second supportmoves with respect to the first support; a rolling contact surface onsaid disk including a beveled portion tapering from one side toward theother and meeting a cutting portion radially projected beyond the planeof the bevel; said disk being held in said first support in cantedposition with respect to a tangent plane at the circumference of the logand said disk being toed in with respect to the line of the travel ofsaid log.

4. Apparatus for removing bark from a log comprising: a first supportand a second support moveable linearly with respect thereto; said secondsupport constructed to receive and firmly hold a workpiece portion of alog with the bark in place on the log as grown, positioned with thelongitudinal axis of the log substantially parallel to the line ofmovement between said first and second supports; a disk carried by saidfirst support in a position of rolling contact with said log, rollingwithout external rotative power supply on the log as the second supportmoves with respect to the first support; a rolling contact surface onsaid disk including a beveled portion tapering from one side toward theother and meeting a cutting portion projecting beyond the plane of thebevel; said disk being held in said first support in canted positionwith respect to a tangent plane at the circumference of the log and saiddisk being toed in with respect to the line of the travel of said log.

5. Apparatus for removing bark from a log comprising: a first supportand a second support movable linearly with respect thereto; said secondsupport member constructed to receive and firmly hold a workpieceportion of a log having the bark in place on the log as grown, inposition with the longitudinal axis of the log substantially parallel tothe line of movement between said first and second supports; adiskcarried by said first support in a position of rollingcontact onsaid log portion as said second support moves with respect to said firstsupport; a rolling contact surfaceon said disk including a beveledportion tapering from one side toward the other and meeting a cuttingportion; the axis of rotation of said diskgbeing held in said firstsupport at a position to tilt and toe in the radial'plane of said diskwith respect to a longitudinal plane radially through said workpiece atthe point of disk contact therewith.

6. Apparatus for removing bark from a log comprising: a first supportand a second support movable linearly with respect thereto; said secondsupport constructed to receive and rigidly hold a workpiece portion of alog having the bark in place on the log as grown, in position with thelongitudinal axis of the log substantially parallel to the line ofmovement between said first and second supports; a disk carried by saidfirst support in a position of rolling contact on said log portion assaid second support moves with respect to said first support; a rollingcontact surface on said disk including a beveled portion tapering at alarge acute angle from one side toward the other and meeting a cuttingportion; the axis of rotation of said disk being held in said firstsupport at a position to tilt and toe in the radial plane of said diskwith respect to a longitudinal plane radially through said workpiece atthe point of disk contact therewith.

7. Apparatus for removing bark from a log according to claim 6 whereinsaid rolling contact surface on said disk is beveled at a large acuteangle on one side only.

8. Apparatus for removing bark from a log comprising: a first supportand a second support movable linearly with respect thereto; said secondsupport constructed to receive and firmly hold a workpiece portion of alog having the bark in position on the log as grown, in position withthe longitudinal axis of the log substantially parallel to the line ofmovement between said first and second supports; a disk carried by saidfirst support in a position of rolling contact on said log and rollingby frictional resistance on the bark of said log as the second supportmoves with respect to the first support; a rolling contact surface onsaid disk including a beveled portion tapering from one side toward theother and meeting a cutting portion; the axis of rotation of said diskbeing held in said lrrst support at a position to tilt and toe in theradial plane of said disk with respect to a longitudinal plane radiallythrough said workpiece at the point of disk contact therewith.

9. Apparatus for removing bark from a log according to claim 8 whereinsaid beveled portion tapers from one side toward the other at a largeacute angle.

10. Apparatus for removing bark from a log according to claim 9 whereinsaid tapering beveled portion tapers trom one side only at a large acuteangle.

11. Apparatus for removing bark from a log comprising: a first supportand a second support movable linearly with respect thereto; said secondsupport constructed to receive and firmly hold a workpiece portion of alog having the bark in position on the log as grown, in position withthe longitudinal axis of the log substantially parallel to the line ofmovement between said first and second supports; a disk carried by saidfirst support in a position of rolling contact on said log and rollingby frictional resistance on the bark of said log as the second supportmoves with respect to the first support; a rolling contact surface onsaid disk tapering from one side toward the other at an acute angle ofabout 70 degrees with respect to the radial plane of the disk andmeeting a cutting portion extending beyond the face of the beveledportion about the width of the disk; the axis of rotation of said diskbeing held in said first support at a position to tilt and toe in theradial plane of said disk with respect to a longitudinal plane radiallythrough said workpiece at the point of disk contact therewith.

12. In a debarking apparatus a slitter disk rotatively carriedimposition for rolling contact on a portion of a log having bark, byfrictional'resistance on the surface of said bark, said disk having arolling contact surface including a beveled portion tapering from oneside toward the other and meeting a cutting portion protruding radiallybeyond the beveled portion of said disk.

13. In a debarking apparatus, the improvement C0111- prising a slitterdisk rotatively carried by said apparatus in position for rollingcontact by frictional resistance on the bark of a workpiece to bedebarked, said disk having a rolling Contact surface including a beveledportion tapering from only one side toward the other at an angle ofabout 70 degrees with the radial plane of the disk and meeting a cuttingportion extending beyond the bev- 8 eled surface of the disk for adistance of about of the width of the disk.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,765 Pauley et a1. Jan. 5, 1954 1,673,265 Pangborn June 12, 19281,887,908 Tidblad Nov. 15, 1932 2,452,631 Cameron Nov. 2, 1948 102,684,098 Graham et al. July 20, 1954 FOREIGN PATENTS 154,716 SwedenJune 5, 1956

